1. Field of the Invention
Example embodiments generally relate to an image scanner and an image forming apparatus, and more particularly, to an image scanner for reading an image on an original and an image forming apparatus incorporating the image scanner.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium according to image data created by an image scanner that scans an image on an original. Such image scanner may be configured to read an image on either a stationary original placed on an exposure glass or a moving original moving over a glass strip.
For example, as shown in FIG. 1, a related-art image scanner 2R includes an exposure glass 21 on which a stationary original is placed stationarily and a glass strip 22 over which a moving original conveyed from an original tray 91 moves. A single reader 23 movable under the exposure glass 21 and the glass strip 22 reads an image on the stationary original and an image on the moving original. In order to read the image on the moving original, the reader 23 moves from a home position below the exposure glass 21 to a moving original reading position below the glass strip 22. As the reader 23 halts at the moving original reading position, the reader 23 reads the image on the moving original moving over the glass strip 22.
The image scanner 2R may be connected to an auto document feeder (ADF) 120 that loads and feeds a plurality of originals successively. Since rigid originals such as cards are not bent flexibly, a straight conveyance path 101 extends from the original tray 91 to an output tray to convey the rigid originals straight without bending them. The straight conveyance path 101 is provided with a conveyance roller pair 97 situated upstream from the glass strip 22 and a conveyance roller pair 98 situated downstream from the glass strip 22 in an original conveyance direction, which convey the original over the glass strip 22. In order to prohibit the conveyance roller pair 97 from striking the exposure glass 21, the glass strip 22 constituting the straight conveyance path 101 is tilted with respect to the exposure glass 21.
Since the glass strip 22 is tilted relative to the exposure glass 21, if the reader 23 moves horizontally from the home position below the exposure glass 21 to the moving original reading position below the glass strip 22, the vertical distance between the reader 23 and the glass strip 22 is greater than that between the reader 23 and the exposure glass 21. The difference between those distances may degrade performance of the reader 23 that reads the image on the stationary original placed on the exposure glass 21 and the image on the moving original moving over the glass strip 22.
Additionally, since the exposure glass 21 is parallel to the reader 23, light emitted from the reader 23 irradiates the stationary original placed on the exposure glass 21 vertically. Conversely, the glass strip 22 tilted relative to the exposure glass 21 is also tilted relative to the reader 23. Accordingly, the optical axis of light emitted from the reader 23 to the moving original moving over the glass strip 22 is not perpendicular to the glass strip 22, thus degrading performance of the reader 23 that reads the image on the moving original moving over the glass strip 22.